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Clinical Neurology > Parasites of the CNS > Flashcards

Parasites of the CNS Flashcards

1
Q

You are presented with a horse that is:

  • Stumbling and falling over the past week
  • Is unsteady in its hindlimbs
  • Has slight wear on the dorsum of its toes on the hindlimbs, so dragging its feet
  • has left-sided gluteal muscle atrophy
  • was able to be pulled to the left on the tail-pull test
  • No cranial nerve deficits

Most common Presentation are the 3A’s: Asymmetric, Ataxic and focal muscle Atrophy

You suspect a parasitic infection, what is the possible etiology?

A

Sarcocystis neurona = equine protozoal myeloencephalitis (EPM)

This is an apicomplexa parasite

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2
Q

How can you confirm the presence of Sarcocystis neurona?

A

1) Immunoblot analysis
- S. neurona antibodies in serum and CSF
CSF: Sn and Sp of 89%
Serum: Sn of 89% and Sp of 71%

2) ELISA: Highly specific for S.neurona specific antibodies
note: You cannot do a PCR, its sensitivity is very low as Merozoites are not found in the CSF, and any free parasite DNA floating around is rapidly destroyed
3) PM: Acute hemorrhagic lesions and necrosis in the spinal cord

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3
Q

What is the Final Host to S. neurona ?

A

Opossum

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4
Q

What are the Intermediate hosts to S. neurona ?

A
  • Domestic Cat

- Several wildlife species including raccoons, skunks, armadillo

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5
Q

What is the Aberrant (“dead-end”) host to S. neurona ?

A
  • Horse
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6
Q

Where does Schizogony occur in the horse?

A

Muscle tissue, producing merozoites

Merozoites penetrate and infect neural tissue

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7
Q

What is treatment for S. neurona in horses?

A
  • Ideal drug: Ponazuril: Antiprotozoal Oral Paste, 5mg/kg/day ~28 days
  • Sulfonamides: Sulfadiazine orally, 20mg/kg
  • Diclazuril and Toltrazuril: coccidiostat that kills parasites in early stages, used as a prophylactic
  • NSAIDs
  • Vitamin E

Caution: steroids are contraindicated in this case

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8
Q

How can S. neurona infection be prevented?

A
  • Prevention is best
  • Keep feed rooms and containers closed and sealed
  • Prevent wildlife from getting into feed room
  • Discard dropped grain to discourage birds/ scavengers
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9
Q

What is the Definitive/ Final Host of Neospora. caninum ?

A
  • Dogs (incl dingo, coyotes and wolves)

NOT foxes! Cant blame them

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10
Q

What is the Intermediate host of Neospora caninum ?

A
  • Mammals and birds

- Cattle being the main issue

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11
Q

Why is Neospora caninum important in cattle?

A
  • Highly prevalent

- Causes 10-45% of abortions

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12
Q

How do dogs or other wild canids get Neospora caninum ?

A
  • Eating tissue cyst infected meat/ placental tissue = exogenous transmission
  • transmission via placenta or milk to puppies (usually the litter is all affected)
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13
Q

How do cattle get Neospora. caninum ?

A
  • Eating infected food (silage or pasture) with oocysts = exogenous transmission
  • Vertical transmission from cow to calf = endogenous transmission
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14
Q

Is Neospora. caninum transmissible to humans? (i.e. zoonotic)

A

No

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15
Q

How does Neospora. caninum affect the cow fetus?

A
  • Multiplying tachyzoites cause cell necrosis in the fetal macrophages, neutrophils, spinal fluid, and other neural cells
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16
Q

How does Neospora. caninum affect the adult/ mature cow?

A
  • Little or no pathology, unless immunocompromised
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17
Q

What will happen to a cow fetus if infected with Neospora. caninum early in gestation?

A
  • Abortion
18
Q

What will happen to a cow fetus if infected with Neospora. caninum mid to late gestation?

A
  • Variety of congenital defects including neurological signs, myocarditis, ataxia, exopthalmia
  • Can be born normal and be a persistent shedder
  • Can be born normal and uninfected

Clinical signs will vary according to:

  • Quantity and duration of parasitemia
  • Effectiveness of maternal immune response
  • Ability of fetus to mount an immune response
19
Q

What usually has to happen in order for a dog to present with clinical signs of Neospora caninum?

A

Immunosuppression

Therefore presentation is as follow:

  • Presents in puppies due to weak immune system
  • Presents in dogs concurrently infected with Canine distemper or Ehrlichiosis
  • Presents in older dogs with waning immune systems or treatment with steroids
20
Q

What are the clinical signs associated with Neospora caninum in a YOUNG dog?

A
  • Encephalomyelitis: hyperexcitability, depression, paresis/ paralysis, head tilt, seizures
  • Myositis-polyradiculoneuritis: progressive pelvic limb paresis (bilateral, non-painful, rigid pelvic limbs)
21
Q

How can Neospora caninum be diagnosed in a young dog showing neurological clinical signs?

A
  • Clinical signs are a big indicator, especially if multiple littermates are showing signs
  • IgG titer in serum
  • Presence of antibodies in CSF
  • Positive response to appropriate treatment
22
Q

What is the treatment for Neospora. caninum in dogs?

A
  • No perfect drug or combination available

Can try:

  • Trimethoprim sulfadiazine + Pyrimethamine
  • Trimethoprim sulfadiazine + Clindamycin
  • Clindamycin
23
Q

What is the treatment for Neospora. caninum in cattle?

A
  • No effective treatment

- Culling of seropositive stock in the breeding herd

24
Q

What is the Intermediate host of Toxoplasma. gondii?

A
  • Sheep
  • Humans
  • (Warm-blooded animals)
  • NOT common in cattle or horses
25
Q

What can Toxoplasmosis cause in sheep and humans?

A

Abortion is the greatest occurrence

26
Q

How can Toxoplasma be diagnosed in cats?

A
  • Fecal sample, Detection of oocysts in the feces
  • Serology: IgM:IgG ratio but not specific
  • PM: immunohistochemical staining of the brain tissue

note: hematology is non-specific. No single test will give a definitive diagnosis. PCR is not useful

27
Q

How can Toxoplasma be diagnosed in sheep?

A
  • Biopsy
  • Post Mortem
  • Immunohistochemistry
  • PCR
  • Serology
28
Q

How can Toxolpasma be diagnosed in Humans?

A

IgM/ IgG ratio and affinity

29
Q

What is the treatment protocol for Toxoplasmosis in sheep?

A

No satisfactory drug treatment

30
Q

Is there a vaccine for Toxoplasma?

A

Yes, available for sheep, but can be used on goats (extra-labelled)

  • Toxovax (attenuated live vaccine)
  • Toxovax provides good immunity to sheep, give before pregnancy and she is not likely to abort
31
Q

How can Toxoplasma be prevented best in sheep?

A
  • Prevent access of cats to feed and bedding
32
Q

How can Toxoplasma be prevented best in pregnant or immunocompromised humans?

A
  • Avoid contact with cat feces
  • Avoid contact with soil (outdoor cats defecate in)
  • Avoid eating raw or undercooked meat
33
Q

How can Toxoplasma be prevented best in cats?

A
  • Feed only dried or canned or cooked food
  • Keep indoors
  • Frequent cleaning of cat litter
34
Q

What usually has to happen for a cat to show clinical signs when infected with Toxoplasma gondii?
What clinical signs would you look out for?

A

Immunosuppression
- Usually concurrently infected with FIV

Clinical signs: behavioral changes, seizures, ataxia, muscle hyperesthesia, paresis/ paralysis, blindness

35
Q

What is the treatment of Toxoplasmosis in Cats?

A
  • Azithromycin
  • Clindamycin
  • Trimethoprim-sulfa
36
Q

What is the final host of T. multiceps?

A

Dogs and wild canids (fox, jackal)

37
Q

What is the intermediate host of T. multiceps?

A
  • Sheep mainly
  • Goats
  • Deer
  • Cattle
  • Pigs
  • Horses
  • Human (Quite rare)
38
Q

Dogs and wild canids are largely unaffected by the adult T. multiceps tapeworm, however what clinical signs do sheep and other intermediate hosts encounter when infected with the metacestode stage?

A
  • Meningoencephalitis

‘Gid’ or ‘Staggers’ = Head pressing, head tilt, blindness, circling and high stepping gate

Dullness, anorexia, weight loss

39
Q

How can T. multiceps be treated and controlled in sheep, goats and other intermediate hosts?

A
  • Localize and decompress the cyst in the brain

- Treat dogs for tapeworms, and don’t feed dogs undercooked sheep carcass or viscera

40
Q

What clinical signs are associated with Babesia infection in dogs?

A
  • Fever
  • Pale mucous membranes
  • Icterus
  • Haemogloburia
  • Depression
  • Haemoglobinemia
  • Weakness
  • Paddling, ataxia and coma due to the distension of capillaries in the cerebrum/ cerebellum leading to edema
41
Q

How can Babesia be diagnosed in dogs?

A
  • Blood smear stained with Giemsa stain
  • ELISA or IFAT
  • PCR
  • PM lesions: splenomegaly
42
Q

How is Babesia transmitted to dogs?

A

Brown dog tick and Ornate Cow Tick

Both not found in Ireland, BUT are found in other areas of Europe and America

Clinical Neurology (17 decks)

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